Neuroinflammatory role of prostaglandins during experimental meningitis: evidence suggestive of an in vivo relationship between nitric oxide and prostaglandins

Palmitic Acid Modulates Microglial Cell Response to Metabolic Endotoxemia in an In Vitro Study

Metabolic endotoxemia (ME) is characterized by a 2-3-fold increase in blood endotoxin levels and low-grade systemic inflammation without apparent infection. ME is usually accompanied by metabolic syndrome, characterized by central obesity and hyperlipidemia. According to numerous studies, ME may lead to functional brain disorders, including cognitive decline, depression, and dementia. In the current in vitro study, we aimed to determine the direct and indirect impact of endotoxin (LPS) and palmitic acid (PA), representing saturated fatty acids, on the inflammatory and oxidative stress response in the human microglial HMC3 cells unstimulated and stimulated with IFNγ. The study's results revealed that direct HMC3 cell exposition to endotoxin and PA increased inflammatory response measured as levels of IL-6 and MCP-1 released into the medium and PGE2 levels in cell lysates. Moreover, direct HMC3 cell treatment with PA and LPS induced oxidative stress, i.e., ROS and COX-2 production and lipid peroxidation. On the contrary, an indirect effect of LPS and PA on microglial cells, assessed as the impact of macrophage metabolites, was much lower regarding the inflammatory response, although still associated with oxidative stress. Interestingly, IFNγ had a protective effect on microglial cells, reducing the production of pro-inflammatory mediators and oxidative stress in HMC3 cells treated directly and indirectly with LPS and PA.

Beneficial Effects of Ibuprofen on Pentylenetetrazol-induced Convulsion

Ibuprofen is a non-steroidal anti-inflammatory drug (NSAID) that is commonly used as an anti-inflammatory, anti-pyretic, and analgesic. Although some studies have focused on the anti-inflammatory and anti-pyretic properties of ibuprofen during febrile convulsions, only one has investigated its antiepileptic effects. In the present study, we aimed to investigate the effects of ibuprofen in rats exposed to pentylenetetrazol (PTZ)-induced seizures. In total, 48 rats were randomly divided in two groups: Group A for electroencephalography (EEG) recordings and Group B for behavioral assessment. All EEG recordings and behavioral assessment protocols were performed. In addition, groups were compared in terms of prostaglandin F2 alfa (PGF2α) levels in the brain. We demonstrated the beneficial effects of the administration of ibuprofen in PTZ-induced seizures in rats via the following findings: spike percentages and Racine convulsion scale values were significantly lower and first myoclonic jerk (FMJ) onset times were significantly higher in the ibuprofen-administered groups. Moreover, PGF2α levels in the brain were significantly higher in the saline and PTZ 70 mg/kg group than in the control and PTZ 70 mg/kg and 400 mg/kg ibuprofen groups. Our study is the first to demonstrate the beneficial effects of ibuprofen on seizures through behavioral, EEG, and PGF2α brain assessments. Ibuprofen can be used for epilepsy and febrile seizures safely and without inducing seizures. However, further experimental and clinical studies are needed to confirm our results.

IDO, COX and iNOS have an important role in the proliferation of Neospora caninum in neuron/glia co-cultures

Central nervous system (CNS) is the main site for encystment of Neospora caninum in different animal species. In this tissue, glial cells (astrocytes and microglia) modulate responses to aggression in order to preserve homeostasis and neuronal function. Previous data showed that when primary cultures of glial cells are infected with N. caninum, they develop gliosis and the immune response is characterized by the release of TNF and IL-10, followed by the control of parasite proliferation. In order to elucidate this control, three enzymatic systems involved in parasite-versus-host interactions were observed on a model of neuron/glia co/cultures obtained from rat brains. Indoleamine 2,3-dioxygenase (IDO), induced nitric oxide synthase (iNOS) responsible for the catabolism of tryptophan and arginine, respectively, and cycloxigenase (COX) were studied comparing their modulation by respective inhibitors with the number of tachyzoites or the immune response measured by the release of IL-10 and TNF. Cells were treated with the inhibitors of iNOS (1.5 mM L-NAME), IDO (1 mM 1-methyl tryptophan), COX-1 (1 μM indomethacin) and COX-2 (1 μM nimesulide) before infection with tachyzoites of N. caninum (1:1 cell: parasite). After 72 h of infection, immunocytochemistry showed astrogliosis and a significant increase in the number and length of neurites, compared with uninfected co-cultures, while an increase of IL-10 and TNF was verified. N. caninum did not change iNOS activity, but the inhibition of the basal levels of this enzyme stimulated parasite proliferation. Additionally, a significant increase of about 40% was verified in the IDO activity, whose inhibition caused 1.2-fold increase in parasitic growth. For COX-2 activity, infection of cultures stimulated a significant increase in release of PGE₂ and its inhibition by nimesulide allowed the parasitic growth. These data indicate that iNOS, IDO and COX-2 control the proliferation of N. caninum in this in vitro model. On the other hand, the release of IL-10 by glia besides modulating the inflammation also allow the continuity of parasitism.

Therapeutic potential to reduce brain injury in growth restricted newborns

Brain injury in intrauterine growth restricted (IUGR) infants is a major contributing factor to morbidity and mortality worldwide. Adverse outcomes range from mild learning difficulties, to attention difficulties, neurobehavioral issues, cerebral palsy, epilepsy, and other cognitive and psychiatric disorders. While the use of medication to ameliorate neurological deficits in IUGR neonates has been identified as warranting urgent research for several years, few trials have been reported. This review summarises clinical trials focusing on brain protection in the IUGR newborn as well as therapeutic interventions trialled in animal models of IUGR. Therapeutically targeting mechanisms of brain injury in the IUGR neonate is fundamental to improving long-term neurodevelopmental outcomes. Inflammation is a key mechanism in neonatal brain injury; and therefore an appealing target. Ibuprofen, an anti-inflammatory drug currently used in the preterm neonate, may be a potential therapeutic candidate to treat brain injury in the IUGR neonate. To better understand the potential of ibuprofen and other therapeutic agents to be neuroprotective in the IUGR neonate, long-term follow-up information of neurodevelopmental outcomes must be studied. Where agents such as ibuprofen are shown to be effective, have a good safety profile and are relatively inexpensive, they can be widely adopted and lead to improved outcomes.

Differential S-nitrosylation of proteins in Alzheimer's disease

Numerous studies have provided evidence regarding the involvement of protein S-nitrosylation in the progression of Alzheimer's disease (AD) pathology and its implication in the formation and accumulation of misfolded protein aggregates. The identification of S-nitrosylated proteins can be a major step toward the understanding of mechanisms leading to neuronal degeneration. The present study targeted S-nitrosylated proteins in AD hippocampus, substantia nigra and cortex using the following work-flow that combines S-nitrosothiol-specific antibody detection, classical biotin switch method labeled with fluorescence dye followed by electrospray ionization quadrupole time of flight tandem MS (ESI-QTOF MS/MS) identification. Endogenous nitrosocysteines were identified in 45 proteins, mainly involved in metabolism, signaling pathways, apoptosis and redox regulation as assigned by REACTOME and KEGG pathway database analysis. Superoxide dismutase (SOD2) [Mn], fructose-bisphosphate aldolase C (ALDOC) and voltage-dependent anion-selective channel protein 2 (VDAC2) showed differential S-nitrosylation signal, not previously reported in AD regions. Extensive neuronal atrophy with increased protein S-nitrosylation in AD regions is also evident from immunofluorescence studies using S-nitrosocysteine antibody. A number of plausible cysteine modification sites were predicted via Group-based Prediction System-S-nitrosothiols (GPS-SNO) 1.0 while STRING 8.3 analysis revealed functional annotations in the modified proteins. The findings are helpful in characterization of functional abnormalities and may facilitate the understanding of molecular mechanisms and biological function of S-nitrosylation in AD pathology.

Modified Wu-Zi-Yan-Zong prescription, a traditional Chinese polyherbal formula, suppresses lipopolysaccharide-induced neuroinflammatory processes in rat astrocytes via NF-κB and JNK/p38 MAPK signaling pathways

Neuroinflammation plays an important role in several neurodegenerative diseases. In this study, we investigated the anti-inflammatory properties of modified Wu-Zi-Yan-Zong prescription (MWP), a traditional Chinese polyherbal formula, in primary cultured rat astrocytes treated with lipopolysaccharide (LPS). The results showed that MWP significantly inhibited release of nitric oxide (NO) and prostaglandin E (PGE), as well as expressions of inducible nitric oxide synthase (iNOS) and cyclooxygenase (COX)-2 in LPS-induced rat astrocytes. Mechanism study indicated that MWP significantly inhibited nuclear factor-kappa B (NF-κB) inflammatory signaling pathway through attenuating inhibitor of nuclear factor-κB (IκB) degradation and down-regulating IκB kinases (IKKs) phosphorylation level. Moreover, MWP also decreased c-Jun NH(2)-terminal kinase (JNK)/p38 mitogen-activated protein kinase (MAPK) phosphorylation, which play an important role in the induction of proinflammatory gene expressions. At last, MWP protected neurons from LPS-activated astrocytes in neuron-astrocyte co-culture system. Taken together, our results suggest that MWP may act to suppress neuroinflammatory response in LPS-stimulated rat astrocytes via NF-κB and JNK/p38 MAPK signaling cascades, and MWP may be a useful agent for prevention and treatment of neuroinflammatory disease.

Differential effects of nitric oxide on blood-brain barrier integrity and cerebral blood flow in intracerebral C6 gliomas

Nitric oxide (NO) signaling in tumors and endothelial cells regulates vascular permeability and blood flow and therefore influences tumor uptake and response to therapeutic compounds. As delivery and efficacy of chemotherapy is impaired in CNS neoplasms due to a partially intact blood-brain barrier (BBB), we studied the effects of NO released by the short-acting NO donor disodium 1-[2-(carboxylato)pyrrolidin-1-yl]diazen-1-ium-1,2-diolate methanolate (PROLI/NO) on BBB integrity and blood flow in C6 gliomas using [¹⁴C]-aminoisobutyric acid (AIB) and [¹⁴C]-iodoantipyrine quantitative autoradiography. PROLI/NO selectively increased intratumoral uptake of [¹⁴C]AIB and [¹⁴C]sucrose when given as a 3-minute intracarotid infusion or a 15-minute i.v. infusion (AIB: tumor, K₁ = 68.7 ± 3.2 vs 24.9 ± 0.9 µL g⁻¹ min⁻¹, P < .0001; sucrose, K₁ = 16.9 ± 0.9 vs 11.5 ± 0.9 µL g⁻¹ min⁻¹, P = .0007). This effect was achieved without significant changes in cerebral and tumor blood flow or arterial blood pressure, which indicates that the effect on vascular permeability is independent of changes in vascular tone induced by NO. This effect was mediated by activation of the NO/3',5'-cyclic guanosine monophosphate (cGMP) pathway, as it was blocked by guanylate cyclase inhibition by LY83583 and reproduced by the delivery of 8-bromoguanosine 5'-monophosphate or inhibition of cGMP degradation by the phosphodiesterase inhibitor zaprinast. Inhibition of inducible NO synthase by aminoguanidine or cyclooxygenase inhibition by indometacin or dexamethasone did not reduce the blood-tumor barrier (BTB) response to PROLI/NO. PROLI/NO, and perhaps other NO-donating compounds, can be used to selectively increase BTB permeability in gliomas through the NO/cGMP pathway at doses that do not cause unwanted vasodilatory changes in blood flow and that do not affect the systemic circulation.

Neonatal intrahippocampal immune challenge alters dopamine modulation of prefrontal cortical interneurons in adult rats

BACKGROUND

Among the diverse animal models proposed for schizophrenia, the neonatal ventral hippocampal lesion (NVHL) is one of the most widely used. However, its construct validity can be questioned because there is no evidence of a lesion present in schizophrenia. Other approaches that have tried to capture environmental influences on development include diverse models of maternal infection.

METHODS

As the early postnatal days in rodents are equivalent to the third trimester of human pregnancy in terms of brain development, we decided to test whether a neonatal immune challenge with an injection of the bacterial endotoxin lipopolysaccharide (LPS) into the ventral hippocampus caused deficits in interneuron function similar to those reported for the NVHL.

RESULTS

Neonatal LPS injection caused a persistent elevation in cytokines in several brain regions, deficits in prepulse inhibition of the acoustic startle response, and a loss of the periadolescent maturation in the response of prefrontal cortical fast-spiking interneurons to dopamine.

CONCLUSIONS

The same phenotypes elicited by a NVHL can be obtained with an intrahippocampal immune challenge, suggesting that perinatal environmental factors can affect adult prefrontal interneuron maturation during adolescence.

Nitric oxide dilates rat retinal blood vessels by cyclooxygenase-dependent mechanisms

It has been suggested that nitric oxide (NO) stimulates the cyclooxygenase (COX)-dependent mechanisms in the ocular vasculature; however, the importance of the pathway in regulating retinal circulation in vivo remains to be elucidated. Therefore, we investigated the role of COX-dependent mechanisms in NO-induced vasodilation of retinal blood vessels in thiobutabarbital-anesthetized rats with and without neuronal blockade (tetrodotoxin treatment). Fundus images were captured with a digital camera that was equipped with a special objective lens. The retinal vascular response was assessed by measuring changes in diameter of the retinal blood vessel. The localization of COX and soluble guanylyl cyclase in rat retina was examined using immunohistochemistry. The NO donors (sodium nitroprusside and NOR3) increased the diameter of the retinal blood vessels but decreased systemic blood pressure in a dose-dependent manner. Treatment of rats with indomethacin, a nonselective COX inhibitor, or SC-560, a selective COX-1 inhibitor, markedly attenuated the vasodilation of retinal arterioles, but not the depressor response, to the NO donors. However, both the vascular responses to NO donors were unaffected by the selective COX-2 inhibitors NS-398 and nimesulide. Indomethacin did not change the retinal vascular and depressor responses to hydralazine, 8-(4-chlorophenylthio)-guanosine-3′, 5′-cyclic monophosphate (a membrane-permeable cGMP analog) and 8-(4-chlorophenylthio)-adenosine-3′, 5′-cyclic monophosphate (a membrane-permeable cAMP analog). Treatment with SQ 22536, an adenylyl cyclase inhibitor, but not ODQ, a soluble guanylyl cyclase inhibitor, significantly attenuated the NOR3-induced vasodilation of retinal arterioles. The COX-1 immunoreactivity was found in retinal blood vessels. The retinal blood vessel was faintly stained for soluble guanylyl cyclase, although the apparent immunoreactivities on mesenteric and choroidal blood vessels were observed. These results suggest that NO exerts a substantial part of its dilatory effect via a mechanism that involves COX-1-dependent pathway in rat retinal vasculature.

Clinical and immunopathologic alterations in rhesus macaques affected with globoid cell leukodystrophy

Globoid cell leukodystrophy, or Krabbe's disease, is a severe disorder of the central and peripheral nervous system caused by the absence of galactocerebrosidase (GALC) activity. Herein, we describe the clinical, neuropathological, histochemical, and immunohistological features observed in rhesus macaques affected with Krabbe's disease. Clinical signs included pronounced muscle tremors of head and limbs, difficulty ambulating, ataxia, hypermetria, proprioceptive deficits, and respiratory abnormalities. Histopathologically, all animals presented with evidence of demyelination in the peripheral and central nervous systems and accumulation of mononuclear and multinuclear globoid cells in the cerebral and cerebellar white matter associated with severe gliosis. Using immunohistochemistry and multi-label confocal microscopy, it was determined that globoid cells were CD68+, HAM56+, LN5+, CD163+, IBA-1+, and Glut-5+, suggesting that both peripheral blood-derived monocytes/macrophages and resident parenchymal microglia gave rise to globoid cells. Interestingly, many of the globoid cells and parenchymal microglia with a more ameboid morphology expressed HLA-DR, indicating immune activation. Increased expression of iNOS, TNF-alpha, and IL-1 beta were observed in the affected white matter, colocalizing with globoid cells, activated microglia, and astrocytes. Cytokine mRNA levels revealed markedly increased gene expression of CCL2 in the brain of affected macaques. CCL2-expressing cells were detected throughout the affected white matter, colocalizing with GFAP+ cells and astrocytes. Collectively, these data suggest that dysregulation of monocyte/macrophage/microglia and up-regulation of certain cytokines may contribute to the pathogenesis of Krabbe's disease.

AUF-1 mediates inhibition by nitric oxide of lipopolysaccharide-induced matrix metalloproteinase-9 expression in cultured astrocytes

Neuroinflammatory diseases are associated with increased production of matrix metalloproteinase-9 (MMP-9) and excessive generation of nitric oxide (NO). NO has been reported to have variable effects on MMP-9 gene expression and activation in various cell types. In the present study, we investigated the effect of NOon MMP-9 expression in primary cortical astrocytes. Zymography and real-time PCR showed that lipopolysaccharide (LPS) dramatically increased latent MMP-9 gelatinolytic activity and MMP-9 mRNA expression. By using the NO donor DETA NONOate, we observed a dose-dependent inhibition of MMP-9 induction by LPS. Active forms of MMP-9 were not found by zymography after NO treatment. The MEK1/2 inhibitor U0126 completely inhibited LPS-induced MMP-9, which was partially inhibited by the p38 MAPK inhibitor SB203580. NO had no effect on LPS-stimulated ERK1/2 and p38 MAPK activation, suggesting that the inhibitory action of NO occurs downstream of MAPK cascades. Real-time PCR analysis showed that NO accelerated the degradation of MMP-9 mRNA after LPS induction. Western blotting and pull-down assay demonstrated that NO increased AUF-1 expression as well as its specific binding to the MMP-9 gene 3'-untranslated region. Knockdown of AUF-1 with siRNA partially reversed the inhibitory action of NO on LPS-stimulated MMP-9 induction. We conclude that NO does not activate MMP-9 in astrocyte cultures but reduces LPS-induced MMP-9 expression via accelerating MMP-9 mRNA degradation, which is partially mediated by AUF-1. Our results suggest that elevated NO concentrations may suppress MMP-9 and restrict the inflammatory response in neurodegenerative diseases.

Depletion of iNOS-derived nitric oxide by prostaglandin H synthase-2 in inflammation-activated J774.2 macrophages through lipohydroperoxidase turnover

PGHS-2 (prostaglandin H synthase-2) is induced in mammalian cells by pro-inflammatory cytokines in tandem with iNOS [high-output ('inducible') nitric oxide synthase], and is co-localized with iNOS and nitrotyrosine in human atheroma macrophages. Herein, murine J774.2 macrophages incubated with lipopolysaccharide and interferon gamma showed induction of PGHS-2 and generated NO using iNOS that could be completely depleted by 12(S)-HPETE [12(S)-hydroperoxyeicosatetraenoic acid; 2.4 muM] or hydrogen peroxide (500 microM) (0.42+/-0.084 and 0.38+/-0.02 nmol x min(-1) x 10(6) cells(-1) for HPETE and H2O2 respectively). COS-7 cells transiently transfected with human PGHS-2 also showed HPETE- or H2O2-dependent NO decay (0.44+/-0.016 and 0.20+/-0.04 nmol x min(-1) x 10(6) cells(-1) for 2.4 microM HPETE and 500 microM H2O2 respectively). Finally, purified PGHS-2 consumed NO in the presence of HPETE or H2O2 (168 and 140 microM x min(-1) x microM enzyme(-1) for HPETE and H2O2 respectively), in a haem-dependent manner, with 20 nM enzyme consuming up to 4 microM NO. K(m) (app) values for NO and 15(S)-HPETE were 1.7+/-0.2 and 0.45+/-0.16 microM respectively. These data indicate that PGHS-2 catalytically consumes NO during peroxidase turnover and that pro-inflammatory cytokines simultaneously upregulate NO synthesis and degradation pathways in murine macrophages. Catalytic NO consumption by PGHS-2 represents a novel interaction between NO and PGHS-2 that may impact on the biological effects of NO in vascular signalling and inflammation.

Impairment of blood-cerebrospinal fluid barrier properties by retrovirus-activated T lymphocytes: reduction in cerebrospinal fluid-to-blood efflux of prostaglandin E2

The choroid plexus epithelium forms the interface between the blood and the CSF. In conjunction with the tight junctions restricting the paracellular pathway, polarized specific transport systems in the choroidal epithelium allow a fine regulation of CSF-borne biologically active mediators. The highly vascularized stroma delimited by the choroidal epithelium can be a reservoir for retrovirus-infected or activated immune cells. In this work, new insight in the implication of the blood-CSF barrier in neuroinfectious and inflammatory diseases is provided by using a differentiated cellular model of the choroidal epithelium, exposed to infected T lymphocytes. We demonstrate that T cells activated by a retroviral infection, but not non-infected cells, reduce the transporter-mediated CSF-to-blood efflux of organic anions, in particular that of the potent pro-inflammatory prostaglandin PGE2, via the release of soluble factors. A moderate alteration of the paracellular permeability also occurs. We identified the viral protein Tax, oxygenated free radicals, matrix-metalloproteinases and pro-inflammatory cytokines as active molecules released during the exposure of the epithelium to infected T cells. Among them, tumour necrosis factor and interleukin 1 are directly involved in the mechanism underlying the decrease in some choroidal organic anion efflux. Given the strong involvement of CSF-borne PGE2 in sickness behaviour syndrome, these data suggest that the blood-CSF barrier plays an important role in the pathophysiology of neuroinflammation and neuroinfection, via changes in the transport processes controlling the CSF biodisposition of PGE2.

Role of cyclooxygenase-2 inhibitors in postoperative pain management

Cyclooxygenase (COX)-2 inhibitors are as efficacious as nonselective nonsteroidal anti-inflammatory drugs for the treatment of postoperative pain but have the advantages of a better gastrointestinal side-effect profile as well as a lack of antiplatelet effects. There have been recent concerns regarding the cardiovascular side effects of COX-2 inhibitors. Nonetheless, they remain a valuable option for postoperative pain management. The pharmacology of these agents and available studies are reviewed.

Acute Bacterial Meningitis in Children

Despite advances in recent decades in management, including new and effective antimicrobials, children with bacterial meningitis still incur significant morbidity and mortality. Pathophysiologic processes including colonization and migration of the bacteria to blood, seeding of the meninges, and meningeal and brain inflammation have been largely elucidated, but more specific knowledge could lead to new effective therapies. Outside of the neonatal period, the most common causative organisms have been Haemophilus influenzae, Streptococcus pneumoniae, and Neisseria meningitidis. However, conjugate vaccines, especially the H influenzae type b preparation, have contributed significantly to steep declines in the incidence of meningitis. Optimal management consists of rapid diagnosis and administration of bactericidal antibiotics with properties allowing adequate penetration of the inflamed blood-brain barrier. Recently, development of microbial resistance has resulted in changes to recommended empiric antibiotic regimens. Novel therapies are under investigation; however, until controlled trials can be conducted, these therapies cannot be recommended.

Mechanisms of apoptosis induced by cisplatin in marginal cells in mouse stria vascularis

Degeneration of the stria vascularis (SV) is amongst the major causes of cisplatin (CDDP)-induced hearing impairment. The pathways of apoptosis occurring in the SV due to CDDP were examined using a mouse experimental model. Temporal bones of adult C57BL/6 mice were collected on days 3, 7 and 14 after the local application of CDDP. Terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling assay and immunostaining for apoptosis-related proteins or reactive radical species were employed for analysis. Local application of CDDP caused apoptotic cell death of marginal cells 3 days after CDDP treatment. Immunohistochemical analyses demonstrated activation of caspase-3 and -9, but not -8, and redistribution of cytochrome c in affected marginal cells, indicating a caspase-dependent, mitochondrion-mediated apoptotic pathway in marginal cells. Temporary expression of hydroxynonenal, nitrotyrosine and inducible nitric oxide synthase in the SV was observed at the induction of apoptosis in marginal cells. CDDP toxicity generates reactive radical species in the SV, which causes mitochondrial membrane permeabilization leading to apoptosis of marginal cells.

Effects of neuroinflammation on glia-glia gap junctional intercellular communication: a perspective

Gap junctions serve as intercellular conduits that allow for the direct transfer of small molecular weight molecules (up to 1 kDa) including ions involved in cellular excitability, metabolic precursors, and second messengers. The observation of extensive intercellular coupling and large numbers of gap junctions in the central nervous system (CNS) suggests a syncytium-like organization of glial compartments. Inflammation is a hallmark of various CNS diseases such as bacterial and viral infections, multiple sclerosis, Alzheimer's disease, and cerebral ischemia. A general consequence of brain inflammation is reactive gliosis typified by astrocyte hypertrophy and proliferation of astrocytes and microglia. Changes in gap junction intercellular communication as reflected by alterations in dye coupling and connexin expression have been associated with numerous CNS inflammatory diseases, which may have dramatic implications on the survival of neuronal and glial populations in the context of neuroinflammation. A review of the effects of inflammatory products on glia-glia gap junctional communication and glial glutamate release is presented. In addition, the hypothesis of a "syncytial switch" based upon differential regulation of gap junction expression in astrocytes and microglia during normal CNS homeostasis and neuroinflammation is proposed.

Prostanoids, not reactive oxygen species, mediate COX-2-dependent neurotoxicity

The prostaglandin synthesizing enzyme cyclooxygenase-2 (COX-2) has emerged as a critical pathogenic factor in brain diseases associated with activation of N-methyl-D-aspartate (NMDA) receptors, including stroke and neurodegenerative diseases. However, the COX-2 reaction products responsible for these deleterious effects have not been identified. In particular, the relative contribution to the neurotoxicity of COX-2-derived prostanoids and reactive oxygen species has not been defined. We found that the brain damage produced by direct injection of NMDA into the somatosensory cortex is attenuated by the COX-2 inhibitor NS-398 or in COX-2-null mice, but that the associated production of free radicals is not. Furthermore, COX-2 inhibition reduces the lesions even if the deleterious effects of free radicals are eliminated by the scavenger superoxide dismutase. The protection exerted by NS-398 is counteracted by a stable analog of prostaglandin E2. The findings directly implicate COX-2-derived prostanoids, rather then radicals, in the COX-2-dependent component of the damage mediated by NMDA receptors and strengthen the rationale for using COX-2 inhibitors in the treatment of neurological diseases associated with glutamate neurotoxicity.

In vivo study on cross talk between inducible nitric-oxide synthase and cyclooxygenase in rat gastric mucosa: effect of cyclooxygenase activity on nitric oxide production

The integrity of gastric mucosa during endotoxemia is maintained by the balance of inflammatory mediators, such as prostanoids originated from cyclooxygenase-2 (COX-2) and nitric oxide (NO) from inducible nitric-oxide synthase (iNOS). Thus, we elucidated in vivo cross talk between prostanoids and NO in gastric mucosa during endotoxemia, using an iNOS-specific inhibitor, N-(3-(aminomethyl)benzyl)acetamidine (1400W); a nonspecific COX inhibitor, indomethacin; and a COX-2-specific inhibitor, N-(2-[cyclohexyloxy]-4-nitrophenyl)methanesulfonamide (NS-398). Gastric mucosal NO and prostaglandin E2 (PGE2), a predominant product of COX, expressed as mean +/- S.D. of five rats per group, were assayed by electron paramagnetic resonance spectrometry and enzyme immunoassay technique, respectively. The levels of NO and PGE2 increased gradually up to 6 h after administration of bacterial lipopolysaccharide (LPS) (NO: control, 0.35 +/- 0.16; 6 h, 13.3 +/- 3.3 nmol/g tissue/30 min; and PGE2: control, 288 +/- 16; 6 h, 806 +/- 15 pg/g tissue). Pretreatment with 1400W decreased the increase in NO level without any effect on the PGE2 level (NO, 4.0 +/- 0.4 nmol/g tissue/30 min; PGE2, 788 +/- 26 pg/g tissue). In contrast, treatment with indomethacin and NS-398 inhibited not only PGE2 level but also NO level in a dose-dependent manner without any significant effect on both iNOS and COX protein and mRNA expression. These results demonstrate that in the LPS-treated rat gastric mucosa, PGE2 enhances the release of NO after activation of iNOS, although NO produced by iNOS does not stimulate the release of PGE2 by COXs. The effect of COX activity on iNOS-NO pathway can be important in the regulation of gastric mucosal integrity in inflammatory states.

Prolonged exposure of microglia to lipopolysaccharide modifies the intracellular signaling pathways and selectively promotes prostaglandin E2 synthesis

During inflammatory or degenerative processes microglial cells are likely to be exposed to activating agents that persist in brain parenchyma for prolonged periods. As our knowledge on microglial activation is largely based on in vitro studies in which microglial cultures are activated by a single administration of pro-inflammatory stimuli, we investigated the effects of repeated endotoxin (LPS) challenges on microglial functional state. Primary rat microglial cultures were subjected to one, two or three consecutive LPS-stimulation and the production of tumor necrosis factor-alpha (TNF-alpha), nitric oxide (NO), prostaglandin E2 (PGE2) and 15-deoxy-Delta12,14-PGJ2 (15d-PGJ2) measured. The ability of microglial cells to produce NO, TNF-alpha and 15d-PGJ2 upon the first LPS challenge rapidly declined after the second and the third stimulations, whereas PGE2 synthesis remained constantly elevated. Accordingly, the expression of inducible NO synthase decreased whereas cyclooxygenase-2 and microsomal PGE synthase remained up-regulated. The signaling pathways evoked by single or multiple LPS-stimulation were also profoundly different, when considering the activation of the transcription factors nuclear factor-kappa B and CREB, and of the p38 MAPK. Our observations suggest that prolonged exposure to LPS, and likely other activating agents, induces in microglia a functional state clearly distinct from that triggered by acute stimulation. The progressive down-regulation of pro-inflammatory molecules and the sustained release of PGE2 could have important implications for the resolution of brain inflammation.

High-pressurized orange juice consumption affects plasma vitamin C, antioxidative status and inflammatory markers in healthy humans

We examined the bioavailability of vitamin C in orange juice processed using high pressure (HP) and its effects on plasma levels of vitamin C, uric acid (UA), F2-isoprostanes (8-epiPGF(2alpha)), C-reactive protein (CRP) and prostaglandin E(2) (PGE(2)) in a healthy human population. Subjects (6 men, 6 women) enrolled in the study consumed 500 mL/d of HP orange juice for 14 d, corresponding to an intake of 250 mg of vitamin C. On d 1 of the study, subjects drank the juice in one dose; on d 2 until the end of the study, d 14, they drank 250 mL in the morning and 250 mL in the afternoon. Blood was collected every h for 6 h, on d 1, and then on d 7 and 14 of the study. Baseline plasma vitamin C concentration was higher (P = 0.014) in women (55.8 +/- 3.8 micro mol/L) than in men (42.8 +/- 2.1 micro mol/L). The maximum plasma vitamin C increase occurred 3 h after drinking the juice, and it remained elevated on d 7 and 14. Plasma 8-epiPGF(2alpha) concentration did not differ between men and women at baseline. However, it was lower at the end of the study in both men (P = 0.044) and women (P = 0.034). Plasma levels of vitamin C and 8-epiPGF(2alpha) were inversely correlated (r = -0.615, P = 0.001). Plasma CRP concentrations tended to be lower on d 14 than at baseline in men (P = 0.317) and women (P = 0.235). Plasma PGE(2) was lower at the end of the study in both men and women (P <or= 0.037). Drinking orange juice increases plasma vitamin C, and decreases 8-epiPGF(2alpha) and PGE(2) levels in humans, which may help reduce the risk of chronic diseases.